1. Field of the Invention
The present invention relates to a submarine power cable presenting a high fatigue resistance sheath, an off-shore installation comprising said submarine power cable, and a process of manufacturing said sheath.
2. Description of Related Art
A typical submarine power cable includes an insulated electrical conductor surrounded by a metallic screen, said metallic screen being able to withstand water penetration and any mechanical wear or forces during production, installation and use of said submarine power cable. Generally, the insulation of the insulated electrical conductor is an insulation system comprising a plurality of layers, such as an inner semi-conductive shield, an insulation body and an outer semi-conductive shield.
The submarine power cable can be a dynamic submarine cable or a static submarine cable.
The dynamic submarine cable is mainly suspended underwater. For example it may be connected to floating platforms by means of which oil and/or gas is exploited from sub-sea wells. This cable type may be freely extending in the sea water between two fixing points, for example the platform and the sea bottom, and will therefore be moving with the motions of the sea, including sea currents and wind-induced motions.
Concerning the static submarine cable, this latter is mainly laid on the sea bed. This cable is extended on the sea bottom between two fixing points so that it does not substantially move in comparison with the dynamic submarine cable.
Typically, the submarine power cable is used to transmit electric power of medium or high voltage, wherein medium voltage is referred to as from about 1 kV up to about 40 kV, while high voltage is referred to as from about 40 kV up to about 300 kV or even above that figure. The submarine power cable may be used for either alternative current (AC) or direct current (DC) power.
By way of example, the document EP-A1-1 933 333 describes a submarine power cable comprising a metallic tubular protective sheath as metallic screen, said metallic tubular protective sheath surrounding an insulated electrical conductor.
However, the fatigue strength of said metallic tubular protective sheath is not optimized to protect in a sufficient way the cable from any mechanical wear or forces during its production, installation and use.